public int doFinal(byte[] out,
    int outOff)
close the digest, producing the final digest value. The doFinal
call leaves the digest reset.

 public String getAlgorithmName()
return the algorithm name

 public int getDigestSize()
return the size, in bytes, of the digest produced by this message digest.

 public  void reset()
reset the digest back to it's initial state.

 public  void update(byte in)
update the message digest with a single byte.

 public  void update(byte[] in,
    int inOff,
    int len)
update the message digest with a block of bytes.